Sports Injury Modeling of the Anterior Cruciate Ligament Based on the Intelligent Finite Element Algorithm

In order to solve the problem of sports injury modeling of the anterior cruciate ligament, a method based on the intelligent finite element algorithm is proposed. Considering the transverse isotropy of the ligament, this paper constructs a 3D finite element model of the knee joint based on medical image data. The same ligament constitutive equation was used to fit the parameters of stress-strain mechanical experimental curves of three different anterior cruciate ligaments, and the effects of different anterior cruciate ligament mechanical parameters on kinematics and biomechanical properties of the knee joint were compared. The experimental results show that, in models 1, 2, and 3, the maximum stress values appear in the posterolateral of the femoral attachment area of the ligament, which are 16.24 MPa, 16.36 MPa, and 22.05 MPa, respectively. However, the stress values at the tibial attachment area are 9.80, 13.8, and 13.93 MPa, respectively, and the stress values at the anterolateral part of the middle ligament are 6.36, 11.89, and 12.26 MPa, respectively, which are all smaller than those at the femoral attachment area, which also quantitatively explains the clinical phenomenon that ACL fracture often occurs in the femoral attachment area in practice. Thus, the three-dimensional finite element model of the knee joint highly simulates the structure and material properties of the knee joint. This method proves that the intelligent finite element algorithm can effectively solve the modeling problem of sports injury of the anterior cruciate ligament.

In Vivo biomechanical evaluations of suture anchors for repairing grade 3 superficial medial collateral ligament injury in a porcine model

Purpose: To clarify the biomechanical and radiological outcomes of superficial medial collateral ligament (sMCL) repair using suture anchors in a large animal model. Methods: The right sMCLs of nine male castrated pigs was completely detached at the femoral attachment. sMCL repair surgery was performed using two suture anchors. The same skin incision, sMCL exposure, and immediate wound closure were made at the left knee as a sham surgery. Magnetic resonance imaging was performed preoperatively and 4 weeks after surgery. The structural properties (upper yield load, maximum load, linear stiffness, and elongation at failure) of the femur-sMCL-tibia complex were determined. Results: During tensile testing, all the repaired sMCLs avulsed from the femoral attachment. There were no significant differences in the upper yield load, maximum load, linear stiffness, or elongation at failure between the groups 4 weeks after surgery or in the MRI-derived signal-to-noise quotients (SNQs) at the mid and tibial sMCL. The SNQs differed significantly at the femoral (2.7 ± 1.2 vs 0.3 ± 0.7; P = 0.00064) portions between groups. Conclusion: The injured sMCLs biomechanically recovered after surgery using suture anchors even though the SNQs were higher than those with native contralateral sMCLs. For clinical relevance, sMCL repair of grade 3 sMCL injuries using suture anchors was both safe and successful with less tissue dissection.

Medial collateral ligament reconstruction graft isometry is effected by femoral position more than tibial position

Purpose The purpose of this study was to examine the length change patterns of the native medial structures of the knee and determine the effect on graft length change patterns for different tibial and femoral attachment points for previously described medial reconstructions. Methods Eight cadaveric knee specimens were prepared by removing the skin and subcutaneous fat. The sartorius fascia was divided to allow clear identification of the medial ligamentous structures. Knees were then mounted in a custom-made rig and the quadriceps muscle and the iliotibial tract were loaded, using cables and hanging weights. Threads were mounted between tibial and femoral pins positioned in the anterior, middle, and posterior parts of the attachment sites of the native superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL). Pins were also placed at the attachment sites relating to two commonly used medial reconstructions (Bosworth/Lind and LaPrade). Length changes between the tibiofemoral pin combinations were measured using a rotary encoder as the knee was flexed through an arc of 0–120°. Results With knee flexion, the anterior fibres of the sMCL tightened (increased in length 7.4% ± 2.9%) whilst the posterior fibres slackened (decreased in length 8.3% ± 3.1%). All fibre regions of the POL displayed a uniform lengthening of approximately 25% between 0 and 120° knee flexion. The most isometric tibiofemoral combination was between pins placed representing the middle fibres of the sMCL (Length change = 5.4% ± 2.1% with knee flexion). The simulated sMCL reconstruction that produced the least length change was the Lind/Bosworth reconstruction with the tibial attachment at the insertion of the semitendinosus and the femoral attachment in the posterior part of the native sMCL attachment side (5.4 ± 2.2%). This appeared more isometric than using the attachment positions described for the LaPrade reconstruction (10.0 ± 4.8%). Conclusion The complex behaviour of the native MCL could not be imitated by a single point-to-point combination and surgeons should be aware that small changes in the femoral MCL graft attachment position will significantly effect graft length change patterns. Reconstructing the sMCL with a semitendinosus autograft, left attached distally to its tibial insertion, would appear to have a minimal effect on length change compared to detaching it and using the native tibial attachment site. A POL graft must always be tensioned near extension to avoid capturing the knee or graft failure.

Prominent Resident’s Ridge as a Potential Cause of Anterior Cruciate Ligament Impingement: A Case Report

Introduction: The resident’s ridge is an arthroscopic landmark that is consistent with the anterior border of the anterior cruciate ligament (ACL) femoral attachment. The identification of the landmark allows for accurate graft placement. Case Report: We report a case of a 30-year athletic individual with an ACL-deficient knee, who had an abnormally large resident’s ridge, abutting the midsubstance of the torn ACL; the residual femoral attachment was behind the ridge. Resection and burring of this ridge were needed to expose the posterior aspect of the intercondylar notch; even after bone-patellar tendon-bone graft placement, some additional removal of bone had to be done to reduce graft impingement on this area in extension. Conclusion: Abnormal resident’s ridge may be misleading about the anatomy of the lateral femoral condyle area. Appropriate resection of abnormal bone is the key to the identification of femoral footprint and graft placement. We speculate that this bony projection may even have contributed to the ACL injury, and extra bone had to be removed to minimize subsequent impingement. Keywords: Anterior cruciate ligament reconstruction, resident’s ridge, knee arthroscopy, anterior cruciate ligament impingement, bone-patellar tendon-bone graft.